Bringing B.C. to the present
Mar 1, 1996 12:00 PM, By Keith Clark
A recent sound-system upgrade at B.C. Place, a domed stadium in downtown Vancouver, British Columbia, emphasizes the significant advances in digital audio technology made within the past decade.The 62,000-seat facility serves as home to the B.C. Lions of the Canadian Football League (CFL), as well as hosting a wide range of events, such as trade shows, exhibitions, stage productions and baseball games. It offers two primary seating levels, the upper and lower decks, with luxury boxes and press facilities sandwiched between. Temporary seating can be added, extending the lower level to the floor of the stadium.
When it opened in the early 1980s, B.C. Place offered an audio system that was state-of-the-art for the period. However, a desire for a significant improvement in the intelligibility of amplified speech dictated a substantial upgrade. At the same time, the owner realized that any upgrade should also include a notable increase in the flexibility provided by the system in comparison to its earlier capabilities.
Acentech, an audio consulting firm with headquarters in Cambridge, MA, was contracted to provide the upgrade. This effort was spearheaded by Stephen Siegel, director of audio and video design for the company. Cinema Stage Installations of Ontario, Canada, provided all system installation work.As is often the case, the B.C. Place project had to be done on the fast track to accommodate the building's busy schedule. In fact, final system tuning and commission were completed just hours before the kickoff of a B.C. Lions game.
Computer controlTo address the issue of increased flexibility, Acentech decided a computer-based system would make the most sense. Peavey Electronics had just introduced the MediaMatrix system, which the design team thought would best meet the team's goals in terms not only of flexibility, but also of cost-effectiveness.MediaMatrix replaced 11 racks of signal-processing gear from the prior system. The gear had been responsible for processing for the main system as well as for other areas, such as the concourses, paging and underbalcony - all needs that could be met by MediaMatrix.
"Every type of signal-processing equipment imaginable was in those racks, including equalizers, line and distribution amplifiers, relays, transformers, compressors and more," said Siegel. "Although it was all functioning, it would have been impractical and maybe impossible to reconfigure all of this gear to work with the new system."
The MediaMatrix mainframe comprises a hard drive and a user-defined number of DSP cards that provide complete processing - delay, crossover, equalization, mixing, compression and more - all available in a myriad of choices. Audio and control break-out boxes, each with eight inputs and eight outputs, can be added to accommodate even the most complex input-output requirements.User-definable software for the DSP cards is presented in a convenient Windows format, greatly simplifying system reconfiguration. The Media-Matrix software can be tailored to work with the hardware and meet almost any system need imaginable.
The design team also calculated that MediaMatrix would provide a much faster setup time and offer the ability to reconfigure the system for future events that aren't even in current plans but could occur in the next five years.
"In facing the very difficult time schedule, we weren't really sure if it would be possible to build the level of signal-processing racks required to get this system up and running properly," Siegel added. "So a system that was software-based was preferable because we could tailor the software off-site beforehand and at the same time reduce the amount of rack wiring that was required."
Software toolsMediaMatrix software comes with all of the essentials a designer could want or need to establish, maintain and alter a sound system. Software includes three main portions - design, compile control and troubleshooting - with thousands of suboptions.
For designing the system, the software provides a device menu offering an extensive selection of individual pieces of equipment that can be selected and placed on the screen. Built-in shortcuts allow placement of multiple devices in a quick and orderly manner.
Once devices are placed in the desired configuration, the software's wire mode connects it all together. Each device on the screen includes input and output nodes that represent the actual inputs and outputs of the devices. Multiple devices can be interconnected in a short time frame. Once the system is wired, the design on the screen resembles an easy-to-read CAD drawing of a block diagram. Activating the software's compile command converts the design into an actual sound system.
At this point, the sound system can be adjusted and settings made on each individual device. The operator can simply double-click the mouse on any device in the block diagram to reveal the control surface of the device. These surfaces resemble traditional audio devices, including meters, knobs, faders and buttons, and they also have indicators showing precise settings and control levels. Numerous surfaces can be opened on the same screen, and panels and controls can be rearranged and then saved.
Custom devices to meet specific needs can be created, and the software allows the designer or operator to import architectural plans or photographs of the facility so that controls of certain rooms, parameters for certain loudspeaker clusters and more can easily be checked and altered precisely to fit the space and application.
By copying control surfaces - such as meters, clip lights and indicators - from the devices right on to the block diagram, this diagram becomes an active part of the system. It enables the designer or operator to quickly locate the source of a problem (muted output, overload and others) and make the proper adjustment. Four levels of password protection limit unauthorized access.
Software implementationAcentech had the software for B.C. Place ready to go by installation time, with all possible troubleshooting done beforehand. The graphic package the consultants customized depicts not only the layout of the facility but also each individual loudspeaker group, which allows the operator to turn individual elements off with a click of the computer's mouse.
"Although MediaMatrix handles all signal processing functions, it also allows a creative developer to layer control interface functions on top of the signal processing functions, with the result a simple but elegant graphical user interface," said Siegel.
Once the software was complete, Acentech took it to Vancouver for loading. Installation contractor Cinema Stage Installations had already assembled the MediaMatrix hardware, which includes 18 break-out boxes, numerous DSP cards and the hard drive, which are all located in the system control booth.After software loading, a test signal was fed through from each input to output, with the design team checking to make certain that all signal processing developed off-line was in fact being implemented correctly in the DSP hardware. A few programming errors were discovered but quickly corrected. All signal processing was ready to go, and the amplifiers had not even been connected to the system.
Once the amplifiers and new loudspeaker clusters were linked to MediaMatrix, the time necessary to get the system fully up and running was dramatically shortened. Almost all troubleshooting had been done beforehand, and the designers could charge right into balancing and equalizing the system. Siegel's team even prebalanced the system as much as was possible without measurements.
With the digital signal processing system, changes could be made quickly. For example, after arriving on site, the design team decided that it would be advantageous to align the high-frequency and low-frequency sections of 24 of the 26 main system loudspeaker clusters. The team added 24 delay units via the software and then time-aligned them to the clusters. Siegel points out that this wasn't something they thought of at the office, but it was easily added in the field and at no additional cost to the owner.
MediaMatrix has not radically altered the way the on-site operators use the system. The house mixing console, a Yamaha 916 from the prior system, and the CD players are still the main elements with which the operators are concerned; the computer-control system serves largely to change configurations of the system from one event mode to another or to turn a cluster off in an area of the stadium not in use. A switch, located adjacent to the console, is practically the only dynamic element during football game use. Its contact closure is read by MediaMatrix, which activates or deactivates portions of two clusters firing directly at the playing field.
"MediaMatrix has worked out very well," Siegel said. "We were a little nervous about whether the software could be properly implemented. After all, 140 outputs are feeding various loudspeaker components. But we found the hardware to be very reliable and the software to be a user-friendly package that we quickly developed a lot of confidence in."
Loudspeaker designThree primary goals dictated the main system loudspeaker design. The first goal was to address a lack of directivity that had plagued the old system. The highly reverberant space, which was devoid of acoustical treatment, mandated that sound be focused on just the audience.
Another goal was to somewhat extend the bandwidth. Although the foremost need is speech intelligibility rather than full-range high-fidelity, the program often includes prerecorded music. Finally, more output level was desired to better compete with crowd noise.
The decision of loudspeaker location was fraught with limitations, so a concept similar to the earlier system was used. A total of 24 two-way loudspeaker clusters are suspended in a ring over the seating area, with added coverage from a larger main cluster over what is the 20 yard line for football. Another smaller cluster is located directly opposite. The clusters are suspended from roof cables about 150 feet (45.7 m) from the stadium floor and are housed in custom steel frames specified by Acentech.
"The roof presented one of the significant challenges of this project," said Siegel. "There is little structure to it, and weight limitations are severe. We had to be certain to distribute the roof load evenly and not put too much weight in any one point."
High-frequency loudspeaker components are driven by existing Yamaha P-series amplifiers retained from the old system, with new amplifiers added for extra dynamic with the low-frequency components. All amplifiers are stored in four rooms behind the upper seating deck, as close to the loudspeakers as possible given the structure of the building.
Output and directivityEach of the 24 ring clusters are made up of Electro-Voice HP4020 large-format horns with DH1A compression drivers and two Altec Lansing 817s, dual-15 inch (381 mm) horn-loaded low-frequency loudspeakers. The 40x20 coverage pattern of the horns provided the desired higher output and increased directivity.
Loudspeaker clusters along the ends of the slightly oval-shaped stadium have three HP4020 horns. The top horn covers the top one-third of the upper seating deck, the middle horn covers the remainder of the upper seating deck as well as one-half of the lower deck, and the bottom horn covers the remaining lower-level seats. Clusters along the sides of the stadium have a fourth horn firing down and toward the field, providing foldback-type coverage for cheerleaders and others along the sidelines.
The larger main cluster features a hemispherical arrangement firing toward the long end of the stadium. It is made up of five HP4020 horns and two HP6040 horns in addition to eight of the 817 low-frequency loudspeakers. This cluster can be lowered via an electric winch to about 30 feet (9 m) above the floor. In this mode, it is perfectly suited for reinforcement of stage productions held directly beneath it. The cluster is raised during football games and other events.
This cluster also contains two horns, firing down at the field, that have dual drivers manifolded to maintain high output. The smaller extended cluster, with three HP4020 horns, also includes one horn with dual manifolded drivers covering the field. During the football games, these downward-firing manifolded horns provide sound reinforcement to the field for all of the halftime entertainers and are activated easily using the switch in the operator's booth.
Loudspeakers and amplifiers for all concourse, underbalcony and luxury box sound systems were retained, with the major upgrade coming via implementation of the MediaMatrix system.
Sound successThe owner of B.C. Place has given the new sound system a complete thumbs up because of the notably improved sound quality as well as the high degree of flexibility provided by the MediaMatrix digital signal processing.
The skills of a design firm such as Acentech, combined with this exciting new signal processing, highlights the true advances being made at an astounding rate in the realm of digital technology as it relates to professional audio.